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Quantum entanglement is essential for a variety of new quantum technologies, including secure communications and quantum computing. Researchers at the Max-Planck-Institute for the Science of Light (MPL) have developed a notably effective method for entangling photons with acoustic phonons. Their findings reveal that this type of entanglement is robust against external noise, which has been a major challenge for quantum technologies until now. Their study has recently been published in ›Physical Review Letters‹.
Quantum entanglement occurs when particles become linked in such a way that the state of one instantly affects the state of the other, no matter how far apart they are. This phenomenon is crucial for many applications in quantum technology, such as secure communication and advanced quantum computing. Since photons, the smallest units of light, can travel incredibly fast and carry quantum information, pairing photons through nonlinear optical methods is a well-known technique. Recently, scientists at MPL have explored creating entanglement between quite different systems, like sound waves (phonons) and optical photons. Their proposed method for optoacoustic entanglement utilizes Brillouin scattering, making it notably robust, apt for integration into quantum signal processing, and functional at higher environmental temperatures.
Albert Einstein famously referred to it as “spooky action at a distance,” and entanglement has captivated scientists and thinkers alike because it challenges our understanding of fundamental physics. Quantum correlations can exist even between particles that are widely separated. Practically speaking, quantum entanglement is fundamental to many innovative quantum technologies, especially in optics, where photon entanglement plays a crucial role in secure communication and quantum computing setups. However, photons can be unstable, prompting researchers to seek alternatives for specific purposes like quantum memory and repeaters. One promising option lies in the acoustic domain, where information can be encapsulated in sound waves.
At MPL, researchers have outlined an efficient method for entangling photons with acoustic phonons. In this approach, the photons and phonons traverse the same optical structures, but phonons travel at a slower pace. This mechanism is based on a nonlinear optical effect known as Brillouin-Mandelstam scattering, which enables the coupling of particles operating at very different energy levels.
In their research, the scientists demonstrated that their entanglement scheme can function at temperatures around tens of Kelvin, significantly higher than what traditional methods require, which often need costly equipment like dilution refrigerators. The potential to apply this technique in optical fibers or photonic chips makes it particularly valuable for advancements in contemporary quantum technologies.
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